In order to investigate the tolerance of sunflower to aniline and the use of sunflower in the phytoremediation of aniline wastewater, we measured the effects of aniline stress on the photosynthesis and chlorophyll fluorescence parameters of hydroponic United States Oil Sunflower and the resulting contents of aniline in the wastewater and organs of sunflowers. At the low concentration of aniline (100 mg/L), the net photosynthesis rate, stomatal conductance, and transpiration rate of sunflower were significantly greater (P < 0.05) than that of the control. Meanwhile, fresh weight, the other photosynthesis parameters, and the chlorophyll fluorescence parameters were not significantly different. However, as the concentration of aniline increased, net fresh weight, net photosynthesis rate, maximum quantum yield of PSII, actual photochemical efficiency, and photochemical quenching were reduced, whereas non-photochemical quenching first increased, reaching a maximum at 200 mg/L and then decreasing thereafter. At the high concentration of aniline 500 mg/L, all the sunflowers died. The data indicated that non-stomatal limitation was responsible for the reduced net photosynthesis rate. Sunflower exhibited the greatest aniline removal rate (80.97%) at the low concentration of aniline (100 mg/L). The aniline was mainly accumulated in aboveground parts of the sunflower, and the content of aniline in the leaves increased along with the concentration of aniline in the wastewater. In contrast, the content of aniline in the stems was not significantly affected, and the content of aniline in the roots was low.